1. Technical Field
The present invention relates to an electrooptical apparatus and a method of manufacturing the electrooptical apparatus.
2. Related Art
Recently, as a light emission element, an electrooptical apparatus called an optical writing head of a display or a printer using an organic electroluminescence element (hereinafter, referred to as “organic EL element”) has been actively developed.
A method of manufacturing an electrooptical apparatus varies depending on whether a light emission material composing the organic EL element (hereinafter, referred to as “organic EL material”) is a polymer organic material or a low molecular organic material. In addition, if the organic EL material is the polymer organic material, a liquid droplet discharge method of dissolving or dispersing the organic EL material in a specific solvent to form a liquid composition, discharging the liquid composition from a nozzle of a liquid droplet discharge head to coat the liquid composition on a specific pixel electrode is known. In this case, by providing a barrier rib in the periphery of the pixel electrode, the coated organic material liquid is prevented from being mixed with the liquid composition coated on a pixel electrode disposed at a different position and thus high-definition patterning can be performed.
However, in the liquid droplet discharge method, the solvent in the liquid composition coated on the pixel electrode is rapidly evaporated. Furthermore, the liquid composition coated on the edges (the upper edge, the lower edge, the right edge, and the left edge) of a substrate is more rapidly dried than the liquid composition coated on the center of the substrate, because the partial pressure of the solvent molecules of the liquid composition coated on the edges of the substrate is lower than that of the liquid composition coated on the center of the substrate. Accordingly, in the dry time, there is a difference between the liquid composition coated on the edges of the substrate and the liquid composition coated on the center of the substrate. The dry time difference between the liquid compositions causes unevenness in film thicknesses of layers of the organic EL element in a pixel or between pixels, and thus causes display unevenness such as brightness unevenness. Accordingly, a method of providing a dummy coating region which is not related to the display in the peripheries of the edges of the substrate to widen the coating region and making the vapor pressure of the solvent in the substrate uniform was suggested (See JP-A-2002-222695).
Furthermore, in order to increase light emission efficiency of the organic EL element, an electrooptical apparatus or an optical writing head having a hole injection layer or an electron injection layer provided between a light emission layer or an electrode is known.
However, the dry state of the liquid composition is also affected by the surface state of the barrier rib. Accordingly, although the dummy coating region is provided, if the surface state of the barrier rib is not uniform, it is difficult to form a uniform layer.